Well, they are (somewhat) correct in saying that it will not work because you can't ping your home machine...

Are you running a router/firewall? There is a decent chance that your router/firewall has icmp turned off, hence it does not return ping. Also, if you are running a router/firewall, with about 99% certainty, you are using NAT/PAT. What is the ip of your desktop at home? If it's 10.0.x.x, 192.168.x.x or 172.16.x.x you're NAT'd and have a non-routable private IP. If this is the case, you will have to configure your router/firewall to port forward the ports that PCAnywhere communicates on. I haven't used it in years, but the ports used to be 5631(tcp) and 5632(udp). You can find the correct ports here:

Once you have found the correct ports, you'll have to setup port forwarding on your firewall/router. For example, if the IP of your desktop is 192.168.1.50, you will have to config the firewall/router to forward all traffic sent on tcp 5631 to 192.168.1.50 on port 5631 tcp and also to send all udp 5632 > 192.168.1.50 on port 5632 udp.

Part of the reason your carrier can not help is because the problem is on your end (at home) and has nothing to do with your BB or the tethering svc.